Generally, operation mechanisms for switchgears include those using hydraulic operating power for providing a large output power and those using spring operating force for providing a low to middle output power. The former mechanisms are referred to as hydraulic operation mechanisms, while the latter mechanisms are referred to as spring operation mechanisms. Particularly, arc-extinguishing chambers of arc gas breakers, which are a sort of switchgear, have been downsized in recent years so that accidental electric currents and other fault electric currents can be cut-off with small operating force and hence spring operation mechanisms have been finding applications than ever. High-speed operation capabilities of providing a 2-cycle electric current cut-off effect (cutting an AC within the time of two cycles thereof) are required of gas circuit breakers for ultra-high voltages.
Japanese Patent No. 2,529,264, the entire content of which is incorporated herein by reference, describes a spring operation mechanism that can provide a 2-cycle electric current cut-off effect. The spring operation mechanism is designed to use torsion bars to provide drive force for turning on and off a switch. More specifically, the mechanism is formed as compact one by reciprocating two torsion bars to provide high-speed operation capabilities.
Japanese Patent Application Laid-Open Publication No. 2007-323989, the entire content of which is incorporated herein by reference, describes a spring operation mechanism that can adapt itself not only to 2-cycle electric current cut-off but also to other numbers of cut-off cycles such as 3-cycle cut-off and 5-cycle cut-off.